The present invention relates to a system, for the pneumatic transport of bulk material such as comminuted or powdered solids.
In a more or less conventional installation, shown in German Patent Specification No. 25 50 164, bulk material is transported through a pneumatic conduit conveyor having a parallel secondary gas line which is connected, at selected intervals to the conduit by check and relief valves. The valves are responsive to a difference in pressure between that in the conduit and that in the secondary gas line, occuring for example, from compaction of the bulk material within the conduit or from some other obstruction in the conveyor itself. The valves divert pressurized gas from the secondary line into the conveyor close to the area of the compaction our obstruction to thus effect a targeted clearance of the transport conveyor.
Although it is possible to thus move bulk materials, which are normally difficult to handle, without any problem, the known installation is overtaxed if the bulk materials are of an adhesive, and particularly sticky character and/or have the tendency to deposit themselves on the inside wall of the conduit. With such material, the conduit gradually becomes blocked by the build-up of the material on the wall, which deposit, from time to time flakes off in large blocks, causng a more severe blockage of the conduit. The deposits frequently result in undesirable product mixture particularly when the form or nature of the product, being transported, is changed.
In U.S. Pat. No. 2,478,326, a system is described for transporting bulk materials which have a tendency to adhere to the inside wall of the conduit. In this patent, the conduit consists of a plurality of sections which are connected by flange ends in end to end relationship. Each of the sections consists of a rigid outer and an elastic inner tube wherein the spaces formed between the outer and inner tube are separately linked through respective piping with the pressure and suction side of a pneumatic compressor. The connecting piping is provided with solenoid operated valves so that each space between the inner and outer tubes can be provided with either a higher pressure than that prevailing in the conveyor line itself or is subjected to periodic surges so that elastic inner tube vibrates. The installation described in this U.S. patent is extremely expensive, particularly for very long conveyor lines, without even eliminating the danger of plugs or blockages, as a particular result of the flaking of the wall deposits.
It is the object of the present invention to provide a system for the pneumatic conveying of bulk material which is improved, over the known prior installations with respect to its functional safety and the ability to facilitate the pneumatic transport over extended stretches.
It is a further object of the present invention to provide a pneumatic conveying system capable of handling bulk materials which are normally handled only with great difficulty. In particular, it is the object of the present invention to provide a pneumatic conveying system which automatically recognizes and clears blockages or plugs and which provides a simple measure for preventing the deposit of the bulk material on the inner walls of the conveyor.
It is the further object of the present invention to provide for the recognition and detection of leaks within the conveying system or the creation of excess porosity and/or openings in the elastic inner tube, which as experience has shown can never be completely eliminated, due to the inherent nature of the elastic inner tube material.
The foregoing together with other objects will be apparent from the following disclosure of the present invention.